The game allows players to create a region of land by terraforming, and then to design and build a settlement which can grow into a city. Players can zone different areas of land as commercial, industrial, or residential development, as well as build and maintain public services, transport and utilities. For the success of a city, players must manage its finances, environment, and quality of life for its residents. SimCity 4 introduces night and day cycles and other special effects for the first time in the SimCity series. External tools such as the Building Architect Tool (BAT) allow custom third-party buildings and content to be added to the gameplay.

SimCity 4 was praised for being the second game in the SimCity series to primarily use a 3D engine to render its graphics, the first being SimCity 64 for the discontinued Nintendo64DD. It received widespread acclaim, won several awards, and was one of the top ten selling PC games of 2003.[4] It was however criticized for the difficulty of gameplay and computer performance.

As with previous SimCity titles, SimCity 4 places players in the role of a mayor (or several mayors), tasked with populating and developing tracts of lands into cities, while fulfilling the needs of fellow Sims that live in the cities. Cities are now located in regions that are divided into segments, each of which can be developed. The player has the option of starting the city in a segment of any of three area sizes. In real measurements, the smallest has a length of one kilometer on a side, and the largest has a length of four kilometers on a side.[dead link][5] The size of a region and its layout of segments can be changed in a bitmap file provided for each region.

Neighbor cities play a larger role than in the previous versions of the game. For example, neighbor deals can be established, where a city can exchange resources such as water, electricity, garbage disposal with other cities for money. Players may develop several inter-dependent cities at the same time, eventually populating the entire region.

Upon selecting a specific segment in a region, gameplay is divided into three "modes", god mode, mayor mode, and MySim mode. Mayor and MySim modes become available after establishing a city. The god mode is available before establishing a city, as well as after, but with fewer functions. The unavailable functions can be re-activated later on using cheats.

The first is the God mode, which allows players to design or terraform a selected tract of land where the city will be built. God mode also allows players to trigger disasters, including tornadoes and earthquakes among several others. Players can select an area where a disaster will occur and even control the direction of certain disasters. Most terraforming tools are disabled after the city is named and founded. The player still has some terraforming tools made available in mayor mode, although they become very limited and expensive, and they can still trigger disasters at will. In addition to these abilities, God mode also gives the player tools to reconcile the borders of the cities, so as to fix any discrepancies created during the terraforming process, and a day/night cycle adjustment, so that one can make it always day, always night, or alternate between day or night in accordance with the in-universe game clock. Both the ability to reconcile the city edges and the ability to modify the day/night cycle are available even once the city has been established.

The second of the modes is the mayor mode, where the actual city building is conducted. Several advisors may give advice to the player on how to best manage a city. Players can build transportation networks, which include roads, streets, avenues, highways, railways, subway lines, and bus stations. Players can also terraform and plant trees in this mode, but in a much smaller scale than in god mode. Terraforming in this mode costs money.

Areas of land in this mode can be zoned as residential, commercial or industrial areas in various densities where the city will begin to grow. Agriculture is now a separate industrial zone-type, unlike previous version of SimCity enabling for farms to grow regardless of high land value, so long as there exists demand for agriculture and agricultural zones have been provided. Zones are now automatically aligned towards roads and most buildings must be adjacent to a road in order to function properly; streets are automatically created when zoning on large tracts of land. Buildings are now classified into several wealth levels, zone types, and building size stages, which are affected by the region's population and the city's condition. The game simulates urban decay and gentrification with buildings deteriorating and refurbished accordingly. Buildings originally constructed for occupation by higher wealth tenants can now support lower wealth tenants in the event surrounding factors forces the current tenants to vacate the building; this allows certain buildings to remain in use despite lacking its initial occupants.[6] Buildings and lots can now be constructed on slopes.

A densely populated city including third-party modifications

Other activities that players can do in mayor mode include building civic buildings that need constant funding to work properly, such as schools, hospitals, parks, police stations, jails, and fire stations. These buildings now come in two or more sizes compared to the single, universal types that were used in previous games. Settlements also need public utilities such as electricity with more or less polluting and more or less expensive types of power stations, water pumps, water purification plants, and waste management services. Facilities that had previously provided citywide coverage, such as educational facilities and medical facilities, have now been modified to provide a more limited coverage, as it has been with police stations and fire stations in previous SimCity titles. Funding can now be adjusted for individual buildings rather than having to change the funding to all buildings, allowing users to specify how much money should be spent to supply a service in accordance to the local population. Maintenance expenses for public utility facilities will increase as they age. The maximum output of facilities also decreases as they get older. The rate at which facilities age is dependent on the percentage of its capacity being used and the level of funding being given to it.[7]

The final mode is the MySim mode which enables players to create user-defined Sims, which will live and work in the city the player has created. When moving a Sim into a city, the player can choose from a selection of characters or import others from The Sims. Sims can be killed by certain disasters or catastrophic events, leave the city if conditions are unfavorable, or die of old age. After they die, their "child" sometimes takes over for them by taking their name, house, and job.

Buildings in SimCity 4 borrow heavily from early 20th century architectural styles, particularly Art Deco and Romanesque Revival, while houses can appear in a traditional American Craftsman style. However, there is an additional, more modern, architectural style similar to Houston's architectural style, and a European style that is based on the skyline of Frankfurt, Germany. The construction of new buildings on zoned areas is now animated. There are a number of buildings based on those found in San Francisco, including the Shell Building (appearing as "Wren Insurance"),[8]450 Sutter Street (appearing as "Vu Financial"),[9] and the Pacific Telephone & Telegraph Building also known as 140 New Montgomery Street (as "The Galvin Corp").[10] The May Company store in Los Angeles, now LACMA West, also appears as "Dennis Department Store." The game also includes famous landmarks from various cities, such as the Empire State Building from New York City.

Unlike its predecessors, which used an engine based on 2D isometric graphics and sprites, SimCity 4 primarily uses a 3D engine to render its graphics. The landscape and moving props such as vehicles are modeled as fully polygonal and rotatable 3D objects. Small buildings and props are drawn as flat images, which are pasted onto billboards; polygons with their surface normal facing into the camera. Larger buildings are modeled using a hybrid approach; a simple polygonal model defines the shape of the building, then textures are added to create detail such as doors, windows and rooftop clutter.

Although a 3D engine is used, the camera in SimCity 4 is restricted to a fixed trimetric orthographic projection for performance reasons.[11] Additionally, a simulated city can now be seen at nighttime as well as during daytime. The time of the day does not affect the gameplay.

The game includes over three hours of background music in MP3 format, ranging from three to eight minutes in length.[citation needed] The music is divided between that used in region mode and god mode, and that used in the city view in mayor mode and MySim mode. In addition, the game has a facility for players to use their own music in the game, also divided between the two views. The music, largely composed by Jerry Martin, was also released separately as a soundtrack.

The Building Architect Tool (BAT) is a suite of tools developed for producing custom buildings. The suite consists of three applications: The Building Architect game pack for Gmax, which enabled users to render Gmax models into SimCity 4sprites or props to be imported into the LE; an updated version of the LE; and the standalone Plug-in Manager, which enables users to modify simulation properties for new lots. Several modified versions have been released that have, in effect, served as bug fixes for various problems that had not been discovered before the initial release. First released on February 2004, it enabled the modding community to produce custom buildings and props for SC4. SimCity 4 's Building Architect Tool is similar in function to SimCity 3000 's Building Architect Tool and SimCity 2000 's Urban Renewal Kit; however, previous programs of this kind were created from scratch by Maxis and used completely different interfaces. The SC4 BAT required a third-party application (Gmax) to function and was never bundled with SC4 's or the Rush Hour expansion pack, as SimCity 3000 Unlimited had with its own BAT.

The Lot Editor (LE) is a tool which allows users to edit or design lots for SimCity 4 using available props. Because it was released several months before the BAT as a stand-alone version, users at the time were only capable of producing lots that consisted of built-in props from SC4. The BAT provided users with an updated version of the LE, which rendered the original LE utility obsolete. However, the old version is still made available in the official site.[15]

In addition to official tools, third-party programs were released for further accessibility in editing SimCity 4 contents, potentially allowing users to change the nature of the game itself. Following the release of the Lot Editor, the Network Addon Mod (NAM) and the "BAT" (Building Architect Tool), the majority of add-ons in circulation consist of user-created content; most are buildings and lots, while others include cosmetic changes for terrain, custom vehicles and modifications in the game's behavior. Some even fundamentally change the mechanics of the game. In some cases, both the skills of lot building and modding are combined, producing lots that are capable of affecting a city in a variety of ways. Some third-party content are only available to those with expansion packs or another mod.[16]

Maxis and Electronic Arts have released a total of three patches that improve or fix issues discovered in the original versions of SC4 and Rush Hour (two for the original SC4 and one for Rush Hour). Among other things, the patches contain performance improvements for larger cities and a variety of minor bug fixes. The two pre-Rush Hour patches each fixed errors in the game code that, while not impeding actual gameplay, were previously preventing nearly a third of the Maxis-designed buildings from ever appearing in the game. The first patch fixed the so-called "Houston Tileset Bug" which was leaving one of the game's three tilesets, a collection of contemporary Houston-inspired buildings, completely out of the rotation, meaning that the only buildings from that tileset ever to appear were several smaller variations shared by all three of the game's original tilesets. With the introduction of that patch, it rapidly became apparent that there was another underlying bug that was preventing approximately two dozen of the game's largest buildings from appearing. This issue was fixed in the second patch.[17]

Although not necessarily a "bug", some players complained about the unrealistic pathfinding mechanism; it would often find the shortest route but not the fastest,[18] which often left mass transit and highways relatively unused. A group of third-party addon developers have made mods which have changed this traffic mechanism.

An integer overflow bug is also present in the game. Under certain conditions, the Junior Sports Program and Parks and Recreation expense items will be a negative value – thus adding to the end of month balance instead of reducing it.

A bug in the inter-city commuting algorithm creates a large traffic flow around a quadripoint.[19]

Earlier versions of the game experienced major flaws when operating on computers by Apple using Intel processors. Aspyr released a beta of a patch to fix the problems in 2007, but the patch was never finalized and many bugs remain. Some have a serious impact on playability,[20] including frequent crashes if a city exceeds 95,000 population, flawed display of the water surface, frequent blurring or replacement of objects with random other objects, and an inability to significantly accelerate the vehicle in driving mode that prevents many gameplay features from being unlocked. This issue was partially fixed when an updated version of the game (which is fully compatible with Intel-powered Macintosh computers) was released on the Mac App Store in early 2014; however, some bugs still remain.

Shortly after its release, the PC version of SimCity 4 garnered mainly positive reviews, gaining 84/100 from Metacritic,[27] and an 85.09% overall score from GameRankings.[26]

The game got a 9.2/10 rating at IGN, calling it a "major evolutionary step in the series".[24] The review commented that the addition of the region view mode adds more depth to SimCity 4 and that the gameplay has a "more accurate representation of city planning and maintenance" than of previous titles in the SimCity series.

The game scored an 8.1/10 rating at GameSpot, stating that the game had a "sleek, attractive interface" and "great audio"; it added however that SimCity 4 was "rather rushed" and that the MySim mode "seems like an afterthought". The review concluded that it was a "complex and detailed strategy game", "though not as polished as it could have been".[22]

GameSpy gave the game a score of 75/100, commenting that SimCity 4 is "graphically stunning"; the review also criticized the game for having issues "that will likely kill the game for casual players" including performance and difficulty.[23]

1UP.com rated the game at B+ and praised the region view feature as well as the detail of the graphics which create a "deeper sense of simulation". The review however criticizes SimCity 4 for suffering crashes and performance issues.[21]

Game Freaks 365 reviewed SimCity 4 giving it a 9.3 out of 10. The review stated that SimCity 4 "is a magnificent simulator of how to build, run and manage a city." It went on to say that, "If you want the best of the best then Sim City 4 Deluxe is the only way to go."[30]

SimCity 4 received further reviews after the release of the Macintosh version. The game received a rating of 7.25/10 from InsideMacGames. The review commented that the regional gameplay was a "new and welcome addition" and that it had detailed and realistic graphics; it was also said however that the game was not "revolutionary", had "horrendous bugs", and that the tutorial and manual lacked information.[25]

On September 22, 2003, Maxis released an expansion pack for SimCity 4 dubbed Rush Hour. SimCity 4: Deluxe Edition, a bundle of the original SimCity 4 game and the Rush Hour expansion pack, was released on the same day. On August 25, 2004, Aspyr Media released SimCity 4: Deluxe Edition for Mac OS X. This was followed by a September 4, 2004, release of a Mac OS X version of SimCity 4: Rush Hour.

The expansion pack, among others, enhances the range of transportation facilities such as four lane avenues, as well as allowing the player to trace traffic flow, control vehicles and construct larger civic facilities, and introduces a new range of contemporary European-inspired architecture.

On July 20, 2010, Electronic Arts released the Deluxe Edition (SimCity 4 and its Rush Hour expansion) for digital download on Steam,[31] a digital distribution service by Valve Corporation. The game is also available on GOG.com, Direct2Drive and Impulse as well as EA's own Origin service. On April 10, 2014, Aspyr released an updated version of their port of the Deluxe Edition on the Mac App Store.[32] The updated version includes bug fixes and performance enhancements, native resolution support, and support for the latest versions of OS X.

SimCity kind of worked itself into a corner, [because] we were still appealing to this core SimCity group. It had gotten a little complicated for people who had never played SimCity. We want to take it back to its roots where somebody who had never heard of SimCity can pick it up and enjoy playing it without thinking it was really, really hard.

Will Wright stated in an interview on May 16, 2003, that there would probably be more expansion packs after Rush Hour,[34] but none have ever been released. In another interview on May 22, 2004, Wright stated that Maxis was attempting to work out a "new direction" for SimCity after new versions had become "steadily more complex".[33]